The present invention relates to an ultrasound transceiver device and cooling thereof and, more particularly, but not exclusively to the cooling of such a transceiver device within a small vessel which may be filled with fluid, such as a blood vessel or other body lumen.
Sverdlik et al, in PCT/IL2008/000234, filed Feb. 21, 2008 disclose a method of using ultrasonic energy for surgical procedures. In a procedure for stabilizing blood vessel wall abnormality, ultrasonic heating is carried out of at least a portion of the blood vessel wall having the abnormality. A parameter is monitored relating to a property of at least a portion of the heated portion of the blood vessel wall; and heating is stopped when the monitored parameter changes by a predetermined factor or after the monitored parameter changes at a slow enough rate.
Maguire and Peacock, in EP 1769759 disclose an air backed ultrasonic transceiver. Specifically they disclose an ultrasound transceiver mounted onto a delivery member, such as the elongate body of a catheter shaft, without a support structure bridging between a separation area between the transceiver and the shaft. Mounting flanges extend from either end of the transceiver and are mounted at first and second locations along the catheter shaft such that the transceiver is not in mechanical contact with the catheter shaft between those mounting locations to provide for air backing between the transceiver and the catheter shaft so as to isolate ultrasound transmission radially away from the catheter shaft and toward the tissue surrounding the shaft. In Maguire and Peacock, sealing of the transceiver ensures that body fluids such as blood do not displace the air.
An ultrasound transceiver can in principle be used to provide a high power ultrasound beam that can thermally damage tissues. However the transformation of electrical energy into ultrasound is inefficient and considerable heat is generated at the transceiver. The heat needs to be safely dissipated without causing damage to the blood vessel itself, and standard heat sink structures cannot be used in blood flow because heat exchange fins can damage platelets and cause clotting. In general the transceiver may be expected to heat the artery wall as well as the more distant features it is intended to damage thermally.
Furthermore, ultrasound transceivers are typically ceramics with piezoelectric properties. Ceramics have low thermal conductivity and thus operation at high power causes relatively large heat differentials across the transceiver which often causes cracking.